Electric tool powered by a plurality of battery packs and adapter therefor

ABSTRACT

An electric power tool comprises a main body supporting a tool and an electric motor housed in the main body for driving the tool. A plurality of first battery interfaces is configured to removably receive or attach a plurality of first battery packs and to electrically connect the plurality of attached first battery packs in series with the electric motor. A plurality of indicators is configured to communicate information concerning the respective conditions of the plurality of attached first battery packs. The plurality of indicators is arranged such that all of the indicators are simultaneously viewable by a user of the electric power tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 13/770,332, filed onFeb. 19, 2013, which is a continuation of U.S. Ser. No. 12/888,100 filedon Sep. 22, 2010, now U.S. Pat. No. 8,984,711, which claims priority toJapanese Patent Application No. 2010-029505 filed on Feb. 12, 2010, thecontents of which are hereby incorporated by reference into the presentapplication.

TECHNICAL FIELD

The present invention relates to an electric power tool powered by aplurality of battery packs and an adapter therefor.

DESCRIPTION OF RELATED ART

U.S. Pat. No. 5,028,858 discloses an electric power tool thatsimultaneously uses two battery packs as a power source. In thiselectric power tool, the two battery packs are connected in series sothat a high voltage is supplied to an electric motor of the electricpower tool. As a result, a higher voltage output suitable forpower-intensive operations can be generated, which output is higher thanis possible when only one battery pack is used as the power source.

SUMMARY

When battery packs are connected in series, the battery packs can bedamaged in some situations. For example, when the charge states of thetwo battery packs differ, one battery pack can become over-dischargedand then may be charged by the other battery pack in the reversedirection (i.e. reverse charging). In this case, the over-dischargedbattery pack may be damaged so seriously that it is no longer useable.

In an attempt to avoid this problem, U.S. Pat. No. 5,028,858 disclosedthe use of two light-emitting diodes for indicating the respectivecharge states of the two battery packs. However, even when suchindicators are provided, the battery packs can still be over-dischargedor become overheated unless the user can see the indicators properly andeasily. In particular, when a plurality of indicators is provided, theuser must diligently watch all of the indicators. If the user does notsee an indicator that is indicating an abnormality, because theindicator is located in a position not readily visible to the user, thebattery pack corresponding to the indicator can still be over-dischargedor become overheated.

In one aspect of the present teachings, this problem is addressed byarranging a plurality of indicators configured to indicate at least onecondition of each respective battery pack such that all of theindicators are simultaneously viewable by the electric power tool user.Therefore, the information being communicated by all of the indicatorscan be conveniently and reliably conveyed to the user, such that thelikelihood of a battery abnormality, which is being indicated for one ormore of the battery packs, being overlooked is substantially reduced.

In one embodiment of the present teachings, an electric power toolpreferably comprises a main body supporting a tool and an electric motorhoused in the main body. A plurality of first battery interfaces isprovided and each battery interface is configured to removably receiveor attach one first battery pack. The plurality of first batteryinterfaces electrically connect a plurality of attached first batterypacks in series with the electric motor. A plurality of indicators isprovided and each indicator is configured to indicate at least onecondition of one first battery pack attached to one of the first batteryinterfaces. The plurality of indicators is arranged such that all of theindicators are simultaneously viewable or visible to a single tool user.

With such a power tool, the tool user can conveniently and reliably viewor see all of the indicators simultaneously and thus can visuallyrecognize the respective conditions of the attached battery packssimultaneously. As a result, if an abnormality is indicated by one ormore of the indicators, the tool user can immediately stop the usage ofthe electric power tool and thereby avoid unnecessary, and possiblyirreparable, damage to the battery pack(s).

The present teachings can be applied to any type of cordless electricpower tool, including but not limited to electric power tools forprocessing metals, electric power tools for processing wood, electricpower tools for processing stone, and electric power tools forgardening. Specific examples include, but are not limited to, electricdrills, electric impact and screw drivers, electric impact wrenches,electric grinders, electric circular saws, electric reciprocating saws,electric jig saws, electric band saws, electric hammers, electriccutters, electric chain saws, electric planers, electric nailers(including electric rivet guns), electric staplers, electric shears,electric hedge trimmers, electric lawn clippers, electric lawn mowers,electric brush cutters, electric blowers (leaf blowers), electricflashlights, electric concrete vibrators and electric vacuum cleaners.

In one embodiment of the present teachings, it is preferred that eachbattery pack comprises a plurality of lithium-ion cells and the nominalvoltage of the battery packs is equal to or greater than 7.0 volts, morepreferably equal to or greater than 12.0 volts and even more preferablyequal to or greater than 18.0 volts. Over-discharging and overheatingcan cause significant damage to lithium-ion cells. Consequently, thepresent teachings are advantageous for preventing the lithium-ion cellsfrom over-discharging and becoming overheated, thereby lengthening theservice life of the battery packs.

In another embodiment, an electric power tool that normally operates ata rated voltage of 36 volts is preferably driven by two battery packs,each comprising a plurality of lithium-ion cells and each having anominal voltage of 18 volts. In such an embodiment, the electric powertool having a higher output can be operated with the readily-availablelower-voltage battery packs. Thus, the higher-voltage electric powertool (e.g., a 36 volt tool) can be used even if a correspondinghigh-voltage battery pack (i.e. a 36 volt battery pack) is not availableto the user. Such an embodiment is also advantageous, because thelower-voltage battery pack (e.g., an 18 volt battery pack) can also beused with corresponding lower-voltage power tools (e.g., an 18 volttool), thereby providing greater flexibility and convenience to theuser.

The nominal voltage of a typical lithium-ion cell is 3.6 volts.Therefore, a battery pack having a nominal voltage of 18 volts includesat least five lithium-ion cells connected in series. The battery packhaving a nominal voltage of 18 volts may also include, for example, tenlithium-ion cells, wherein five pairs of lithium-ion cells are connectedin parallel, and the five pairs of parallel-connected lithium-ion cellsare connected in series, whereby a voltage of 18 volts is output. In asimilar manner, a battery pack having a nominal voltage of 18 volts canalso include 15 or more lithium-ion cells by using such parallel- andseries-connected cells. The higher the number of lithium-ion cells, thegreater the capacity of the battery pack and consequently the smallerthe electric current flowing in each lithium-ion cell during dischargeof the battery due to a load being driven thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a group of products according to one embodiment of thepresent teachings;

FIG. 2 shows a high-voltage electric power tool that simultaneously usestwo low-voltage battery packs as a power source;

FIG. 3 is a top view illustrating the two low-voltage battery packsdetached from the main body of the high-voltage electric tool of FIG. 2;

FIG. 4 is a bottom view illustrating the two low-voltage battery packsdetached from the main body of the high-voltage electric tool of FIG. 2;

FIG. 5 is a schematic circuit diagram illustrating an electric circuitof the high-voltage electric tool of FIG. 2;

FIG. 6 is a modified example of the electric circuit of FIG. 5 having abypass circuit added thereto;

FIG. 7 is a modified example of the electric circuit of FIG. 5, in whichthe position of the connection to the power supply circuit for the maincontroller has been changed;

FIG. 8 is a modified example of the electric circuit of FIG. 5, in whichthe position of the connection to the power supply circuit for the maincontroller has been changed and the bypass circuit has been added;

FIG. 9 shows two low-voltage battery packs connected to the main body ofa high-voltage electric tool via an adapter having a cord connecting apack side unit with a main body side unit;

FIG. 10 shows the main body side unit of the adapter of FIG. 9 ingreater detail;

FIG. 11 shows the pack side unit of the adapter of FIG. 9 in greaterdetail;

FIG. 12 is a schematic circuit diagram showing a representative electriccircuit of the adapter of FIGS. 9-11;

FIG. 13 is a modified example of the electric circuit of FIG. 12 havinga bypass circuit added thereto;

FIG. 14 shows two low-voltage battery packs connected to the main bodyof a high-voltage electric tool via an integrated or one-piece adapter;

FIG. 15 shows an upper portion of the integrated adapter of FIG. 14 ingreater detail;

FIG. 16 shows a lower portion of the integrated adapter of FIG. 14 ingreater detail;

FIG. 17 shows a known low-voltage electric tool using one low-voltagebattery pack as a power source;

FIG. 18 is a bottom view corresponding to FIG. 17 after the low-voltagebattery pack has been detached from the main body of the low-voltageelectric tool;

FIG. 19 shows the low-voltage battery pack in greater detail;

FIG. 20 shows a known high-voltage electric tool having one high-voltagebattery pack as a power source;

FIG. 21 is a top view illustrating the high-voltage battery packdetached from the main body of the high-voltage electric tool, and

FIG. 22 is a bottom view illustrating the high-voltage battery packdetached from the main body of the high-voltage electric tool.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exemplary, non-limiting group of cordless power toolproducts according to one embodiment of the present teachings. As shownin FIG. 1, the group of products includes two types of battery packs 10,30, three types of electric power tools 50, 70, 100, and two types ofadapters 200, 300. The “high-voltage” electric power tool 70 is normallyintended to use a single “high-voltage” battery pack 30 as a powersource. However, the adapters 200, 300 may serve to electrically connecta plurality of “low-voltage” battery packs 10 to a main body 72 of theelectric power tool 70 so that the electric power tool 70 is suppliedwith the same or substantially the same voltage as the “high-voltage”battery pack 30.

In the present exemplary embodiment, the first battery pack 10 has anominal voltage of 18 volts and the second battery pack 30 has a nominalvoltage of 36 volts. For the sake of convenience in the followingdescription, the first battery pack 10 having the nominal voltage of 18volts will also be referred to as a “low-voltage battery pack 10” andthe second battery pack 30 having the nominal voltage of 36 volts willalso be referred to as a “high-voltage battery pack 30”.

The low-voltage battery pack 10 comprises (at least) five lithium-ioncells connected in series. The high-voltage battery pack 30 comprises(at least) ten lithium-ion cells connected in series. The two types ofbattery packs 10, 30 are preferably rechargeable using a battery charger(not shown in the figures) after being used as power sources for theelectric tools 50, 70, 100. Further, the two types of battery packs 10,30 are preferably so-called “slide-type” battery packs that are attachedby sliding into or onto corresponding engagement portions of theelectric power tools 50, 70, 100, the adapters 200, 300 or the charger.Such battery packs 10, 30 have already been put to practical use. Inparticular, the low-voltage battery pack 10 with the nominal voltage of18 volts has been widely used. However, the structure of the batterypack connection is not particularly limited and a wide variety ofbattery pack connection mechanisms known in the art also may beadvantageously utilized with the present teachings.

The low-voltage battery pack 10 can incorporate, for example, tenlithium-ion cells, rather than five lithium-ion cells, as was discussedabove at the end of the Summary section. In this case, the tenlithium-ion cells comprise five pairs of lithium-ion cells connected inparallel, and the five pairs of parallel-connected lithium-ion cells areconnected in series to output a voltage of 18 volts. Likewise, thehigh-voltage battery pack 30 can incorporate, for example, twentylithium-ion cells, rather than ten lithium-ion cells. In this case, thetwenty lithium-ion cells comprise ten pairs of lithium-ion cellsconnected in parallel and the ten pairs of parallel-connectedlithium-ion cells are connected in series to output a voltage of 36volts.

In the present exemplary embodiment, the “low-voltage” electric powertool 50 is designed to operate at a nominal voltage of 18 volts and theother two “high-voltage” electric tools 70, 100 are designed to operateat a nominal voltage of 36 volts. For the sake of convenience in thefollowing description, the electric tool 50 operating at the nominalvoltage of 18 volts will be referred to as a “low-voltage electric(power) tool 50”, and the electric tools 70, 100 operating at thenominal voltage of 36 volts will be referred to as “high-voltageelectric (power) tools 70, 100”. As will be understood, however, theterms “low-voltage” and “high-voltage” are relative terms and are merelymeant to indicate that two battery packs, which normally supply currentsat different voltages, and two tools, which normally operate atdifferent voltages, are contemplated by this aspect of the presentteachings. It is not necessary that the high-voltage applications aretwice the voltage of the low-voltage applications or, in fact, are anyparticular multiple thereof. For example, in certain applications of thepresent teachings, two low-voltage (e.g., 18-volt) battery packs 10 maybe connected in series to a higher-voltage electric power tool thatnormally operates at a rated voltage that is not a multiple of thelow-voltage battery packs 10, such as, e.g., 24 volts. In this case,voltage step-down circuitry is preferably provided either in the tool orin an adapter 200, 300 that connects the battery packs 10 to the tool.

As shown in FIG. 17 and FIG. 18, the low-voltage electric tool 50 isdesigned to normally use one low-voltage battery pack 10 as its solepower source. This low-voltage electric tool 50 is for example anelectric impact driver and drives a tool chuck 54 in response to theoperation of a main switch 58. A driver set, which is a tool, can bemounted on the tool chuck 54. Such a low-voltage electric tool 50 hasalready been put to practical use and has been widely sold together withthe low-voltage battery pack 10 having the nominal voltage of 18 volts.

The main body 52 of the low-voltage electric tool 50 includes onebattery interface 60. The battery interface 60 is configured toremovably receive or attach the low-voltage battery pack 10, and thelow-voltage battery pack 10 can be slidably received or attachedtherein. The battery interface 60 has a pair of rails 62, a positiveelectrode input terminal 64 a, a negative electrode input terminal 64 b,and a latch receiving hole 68. A battery controller input/outputterminal is also preferably provided, but is not shown in FIG. 18.

As shown in FIG. 19, the low-voltage battery pack 10 includes aconnector 20 that can be slidingly inserted into the battery interface60. The connector 20 includes a pair of rails 22, a positive electrodeoutput terminal 24 a, a negative electrode output terminal 24 b, and anautostop terminal 26. When the low-voltage battery pack 10 is slidablyattached to the battery interface 60, the positive electrode outputterminal 24 a of the low-voltage battery pack 10 is electricallyconnected to the positive electrode input terminal 64 a of the main body52, and the negative electrode output terminal 24 b of the low-voltagebattery pack 10 is electrically connected to the negative electrodeinput terminal 64 b of the main body 52. In addition, the autostopterminal 26 is connected to the battery controller input/outputterminal. As a result of this sliding connection, the low-voltagebattery pack 10 is also physically connected to the main body 52 of thelow-voltage electric tool 50 and the battery cells 16 (see e.g., FIG. 5)are electrically connected with the internal circuitry of the tool 50.Further, the low-voltage battery pack 10 has a latch member 12 thatengages with the latch receiving hole 68 of the battery interface 60 anddetachably affixes the low-voltage battery pack 10 to the batteryinterface 60. The latch member 12 can be released from the latchreceiving hole 68 by operating a latch release button 14.

The two types of high-voltage electric tools 70, 100 will be explainedbelow. The first high-voltage electric tool 70 is designed to benormally operated using one high-voltage battery pack 30 as the solepower source, as will now be explained with reference to FIGS. 20, 21,and 22. The high-voltage electric tool 70 may be, e.g., an electricblower that includes a blower fan disposed in the main body 72 that isrotatably driven in response to the operation of a main switch 78. Theelectric blower 70 is an electric power tool normally used for gardeningand cleaning-up purposes by propelling air from a tip 73 a of a nozzle73 to move debris, such as dead leaves. The high-voltage electric tool70 operating at a nominal voltage of 36 volts has already been put topractical use together with the high-voltage battery pack 30 thatoutputs a nominal voltage of 36 volts.

Referring to FIG. 22, the main body 72 of the high-voltage electric tool70 has one battery interface 80. The battery interface 80 is configuredto removably attach to the high-voltage battery pack 30, and thehigh-voltage battery pack 30 can be slidably received therein. Thebattery interface 80 includes a pair of rails 82, a positive electrodeinput terminal 84 a, a negative electrode input terminal 84 b, a batterycontroller input/output terminal 86 and a latch receiving hole 88.

The high-voltage battery pack 30 includes a connector 40 that can beslidingly inserted into the battery interface 80, as shown in FIG. 21.The connector 40 includes a pair of rails 42, a positive electrodeoutput terminal 44 a, a negative electrode output terminal 44 b, and anautostop terminal 46. When the high-voltage battery pack 30 is attachedto the battery interface 80, the positive electrode output terminal 44 aof the high-voltage battery pack 30 is connected to the positiveelectrode input terminal 84 a of the battery interface 80, and thenegative electrode output terminal 44 b of the high-voltage battery pack30 is connected to the negative electrode input terminal 84 b of thebattery interface 80. Further, the autostop terminal 46, which iselectrically connected to a controller of the battery pack 30 as will bediscussed further below, is connected to the battery controllerinput/output terminal 86. As a result, the high-voltage battery pack 30is electrically connected to the circuitry inside the main body 72 ofthe high-voltage electric tool 70. Further, the high-voltage batterypack 30 has a latch member 32 that engages with the latch receiving hole88 of the battery interface 80 and detachable affixes the high-voltagebattery pack 30 to the battery interface 80. The latch member 32 can bereleased from the latch receiving hole 88 by operating a latch releasebutton 34.

The connectors 20, 40 of the low-voltage battery pack 10 and thehigh-voltage battery pack 30 may have basically the same or similarstructures. However, the sizes of the connectors 20, 40 may differ,e.g., the spacing between the rails 22, 42 may differ. In this case, thelow-voltage battery pack 10 cannot be attached to the battery interface80 of the high-voltage electric tool 70, and the high-voltage batterypack 30 cannot be attached to the battery interface 60 of thelow-voltage electric tool 50. In other words, due to the sizedifferences in the connectors 20, 40, the battery interface 80 is adedicated interface for the high-voltage battery pack 30, and thebattery interface 60 is a dedicated interface for the low-voltagebattery pack 10. Further, in another embodiment, the interfaces 60, 80may be dedicated, in addition or in the alternative, based upondifferences in the shapes of the connectors 20, 40.

Referring now to FIGS. 2-4, the second high-voltage electric tool 100 isdesigned to be normally operated, on the other hand, by simultaneouslyusing two low-voltage battery packs 10 as its power source. Thehigh-voltage electric tool 100 also may be an electric blower having ablower fan rotatably supported in a main body 102 that is driven inresponse to the operation of a main switch 108. The electric blower 100is basically identical to the above-described electric blower 70 interms of functions and applications thereof.

In order to utilize current simultaneously supplied from two batterypacks 10, the main body 102 of the high-voltage electric tool 100includes two battery interfaces 130. Each battery interface 130 isconfigured to removably and, e.g., slidably, receive or attach onelow-voltage battery pack 10. Each battery interface 130 includes a pairof rails 132, a positive electrode input terminal 134 a, a negativeelectrode input terminal 134 b, a battery controller input/outputterminal 136 and a latch receiving hole 138. The battery interface 130is substantially identical to the battery interface 60 of theabove-described low-voltage electric tool 50 in terms of the respectivestructures. The two battery interfaces 130 are arranged side by side inthe rear portion of the main body 102, and the low-voltage battery packs10 can be inserted in the same direction. The two low-voltage batterypacks 10 attached to the two battery interfaces 130 are connected inseries and supply current to the circuitry of the main body 102 at about36 volts.

The main body 102 of the high-voltage electric tool 100 also includestwo indicators 160 respectively positioned above the two batteryinterfaces 130. Each indicator 160 comprises, e.g., one or morelight-emitting diodes, or another means for visually communicatingbattery condition information to the tool user, such as but not limitedto one or more incandescent lamps and/or a display, such as an LCD. In apreferred embodiment, one of the indicators 160 may indicate a chargestate or level of charge of the low-voltage battery pack 10 attached toone battery interface 130, and the other indicator 160 may indicate thesame condition (i.e. level of charge) or another condition of thelow-voltage battery pack 10 attached to the other battery interface 130.More preferably, both indicators 160 indicate the charge state or thelevel of charge of the corresponding low-voltage battery pack 10. Forexample, the light-emitting diode can be illuminated when the chargestate drops to a level at which recharging of the battery pack 10 isnecessary. It is further preferred that each indicator 160 indicates thecharge state of its corresponding low-voltage battery pack 10 at leastin two levels, e.g., a yellow “low-charge warning” and red “immediatelystop tool use” indication. A third green “tool operation permitted” LEDalso may be optionally provided, so that the tool user can receivevisual confirmation that the battery is in a suitable condition for use.It is also preferred that one or more indicators 160 communicateinformation concerning a possible battery temperature abnormality (e.g.,overheating) of the corresponding low-voltage battery pack 10, insteadof or in addition to the charge state of the corresponding low-voltagebattery pack 10.

As shown in FIG. 2, the two indicators 160 are arranged side by side ona rear surface 102 a of the high-voltage electric tool 100 and have thesame indication direction (that is, the direction of illumination of thetwo light-emitting diodes is the same or substantially the same).Therefore, the user can see both indicators 160 simultaneously and cansimultaneously recognize the respective charge states of the twolow-voltage battery packs 10 in a convenient and reliable manner.Further, the indicators 160 are disposed above the corresponding batteryinterfaces 130. Therefore, for example, if the high-voltage electrictool 100 abruptly stops, the user can immediately and convenientlydetermine which of the low-voltage battery packs 10 has experienced aproblem or abnormality. In addition or in the alternative to the rearsurface 102 a, the two indicators 160 could be disposed in otherlocations that can be simultaneously viewed by the user, such as anupper surface of the main body 102. More particularly, it is preferredthat the two indicators 160 are disposed generally in the same plane, sothat the user can simultaneously see the two indicators 160 from variousdifferent directions.

In addition or in the alternative, one or more indicators 160 can bealso provided on an outer surface of each low-voltage battery pack 10,e.g. a surface of the battery pack 10 that faces rearward when thebattery pack 10 is attached to the tool 100. As was already explainedabove, it is preferred that the two battery interfaces 130 are arrangedside by side and can slidably receive the low-voltage battery packs 10in the same direction. In such an embodiment, when the two low-voltagebattery packs 10 are attached to the main body 102, the two indicators160 will be positioned side by side in the same plane and the indicationor illumination direction thereof will also be the same or substantiallythe same. As a result, even if the indicators 160 are disposed on therespective battery packs 10, the user can simultaneously view the twoindicators 160 from various different directions.

An exemplary electric circuit for the high-voltage electric tool 100, aswell as for the two low-voltage battery packs 10 serving as the powersource for the tool 100, will be explained below with reference to FIG.5. Each low-voltage battery pack 10 comprises five battery cells 16connected in series and a battery controller 18, preferably amicroprocessor. Each cell 16 is preferably a lithium-ion cell and thenominal voltage thereof is 3.6 volts. The five cells 16 connected inseries are connected to the positive electrode output terminal 24 a andnegative electrode output terminal 24 b, and current can flow across thetwo terminals 24 a, 24 b at a voltage of about 18 volts. As shown inFIG. 5, the negative electrode output terminal 24 b of the upperlow-voltage battery pack 10 is electrically connected to the positiveelectrode output terminal 24 a of the lower low-voltage battery pack 10via the terminals 134 a and 134 b, which are conductively connected by awire. As a result, when the two low-voltage battery packs 10 areconnected to the respective battery interfaces 130, the battery cells 16of the two low-voltage (18 volt) battery packs 10 are connected inseries and supply current to the circuitry of the main body 102 at avoltage of about 36 volts.

The battery controller 18 preferably comprises an integrated circuitthat includes a CPU and can execute various programs stored therein. Thebattery controller 18 is electrically connected to each cell 16 and canmeasure the voltage of each cell 16. The battery controller 18 may beprogrammed to perform an algorithm, wherein the controller 18 determinesthe charge state or level of charge of each cell 16 based on themeasured voltage of each cell 16, compares the measured voltage to apredetermined, stored threshold value and then outputs an autostopsignal (AS signal) to the autostop terminal 26 when at least one cell 16is determined to require recharging based upon the comparison step. Inthis case, the autostop signal may be a signal, e.g., indicating that ahigh impedance has been detected. In this embodiment, and all otherembodiments disclosed herein, the autostop signal may preferably be adigital logic signal that is selected from one of two different voltagelevels, i.e. a “1” or “0” digital signal that has a distinctly differentvoltage level signal as compared to a “battery normal” signal. However,it is also contemplated that the battery controller 18 may be an analogcircuit or a mixed analog/digital circuit (e.g., a state machine) andthe battery controller 18 may output analog signals (e.g., signalshaving more than two voltage levels) as the autostop signal. Naturally,the battery controller 18 is not limited to outputting only “autostop”signals, but may also be configured or programmed to output a widevariety of signals, e.g., representing one or more conditions of thebattery, such as battery temperature, battery voltage, batteryimpedance, etc.

The main body 102 is provided with a motor 176 that drives the tool (inthis exemplary embodiment, a blower fan). The two low-voltage batterypacks 10 are connected in series with the motor 176 via a main switch178. The main body 102 is provided with a speed adjusting circuit 190, apower FET 194, a gate-voltage-controlling transistor 192, and a voltagedivision circuit 196. The power FET 194 is connected in series with themotor 176 and can shut off the electric current flowing to the motor176. The speed adjusting circuit 190 performs pulse width modulationcontrol for controlling the current flow through the power FET 194 andthus can adjust the rotational speed of the motor 176 in a manner wellknown in the power tool field. The gate-voltage-controlling transistor192 is connected to the gate of the power FET 194 and, together with thevoltage division circuit 196, can control the gate voltage of the powerFET 194.

The main body 102 is also provided with a main controller 152, a powersupply circuit 142 for the main controller 152, a shunt resistor 150connected in series with the motor 176, a current detection circuit 148that detects the electric current flowing to the motor 176 based on thevoltage of the shunt resistor 150, and an autostop signal (AS signal)input/output circuit 144 that inputs/outputs autostop signals to/fromthe gate-voltage-controlling transistor 192.

The main controller 152 is preferably an integrated circuit including aCPU and can execute various programs stored therein. For example, themain controller 152 may be programmed to perform the followingalgorithm. After receiving a voltage signal outputted by a currentdetection circuit 148 as an input signal, the main controller 152compares the voltage signal to a pre-set, stored threshold/permissiblevalue and then outputs an autostop signal to thegate-voltage-controlling transistor 192 via the autostop signalinput/output circuit 144 when the electric current of the motor 176exceeds the pre-set permissible value. In this case, thegate-voltage-controlling transistor 192 decreases the voltage coupled tothe gate of the power FET 194 to the ground voltage, thereby shuttingoff the power FET 194. As a result, the motor 176 and the low-voltagebattery pack 10 are electrically disconnected and an overload of themotor 176 and the low-voltage battery pack 10 may be prevented. A fuse162 for preventing an excessive current from flowing between the motor176 and the low-voltage battery pack 10 may also optionally be providedin the circuit path between the motor 176 and the low-voltage batterypack 10.

The main controller 152 is electrically connected to the batterycontroller input/output terminal (hereinafter “autostop terminal”) 136of the battery interface 130 and can receive a signal voltage (forexample, an autostop signal) from the battery controller 18 as an inputsignal and can output a signal voltage (for example, a dischargeprotection cancellation signal) to the battery controller 18. In thiscase, because two low-voltage battery packs 10 are connected in series,the reference voltages (ground voltages) of the two low-voltage batterypacks 10 differ from each other. More specifically, whereas thereference voltage of the low-voltage battery pack 10 positioned at thelow-voltage side (lower side in FIG. 5) will be referred to as a zerovolt ground, the reference voltage of the low-voltage battery pack 10positioned at the high-voltage side (upper side in FIG. 5) is 18 voltsdue to the series connection via terminals 24 a, 134 a, 134 b, 24 b. Thereference voltage of the main body 102 is equal to the reference voltageof the low-voltage battery pack 10 at the low-voltage side and is thusalso zero volts. As a result, the levels of the inputted and outputtedsignal voltages differ significantly between the main controller 152 ofthe main body 102 and the battery controller 18 of the upper low-voltagebattery pack 10 positioned at the high-voltage side. Consequently, thesignal voltages cannot be directly inputted and outputted between thecontrollers 18, 152 unless a conversion (e.g., a step-down, step-up orother voltage level shift) of the signal voltages is first performed.

To overcome this problem, the high-voltage electric tool 100 of thepresent embodiment also includes two voltage level-shifters (e.g.,DC-to-DC converters) 154 b, 156 b provided between the batterycontroller 18 of the low-voltage battery pack 10 positioned at thehigh-voltage side and the main controller 152 of the main body 102. Onelevel-shifter 154 b is provided on a conductive path 154 that conducts asignal voltage from the main controller 152 to the battery controller 18and raises, preferably proportionally raises, the level of the signalvoltage outputted by the main controller 152 to an acceptable orreadable level for the battery controller 18. The other level-shifter156 b is provided on a conductive path 156 for conducting a signalvoltage from the battery controller 18 to the main controller 152 andlowers, preferably proportionally lowers, the level of the signalvoltage outputted by the battery controller 18 to an acceptable orreadable level for the main controller 152. As a result, signals can becommunicated (i.e. input and output) between the battery controller 18and the main controller 152 without any problem caused by the differentranges of voltages at which the two controllers 18, 152 operate.

Further, cut-off switches 154 a, 156 a are also provided between eachbattery controller 18 and the main controller 152. One cut-off switch154 a is provided on the conductive path 154 for conducting the signalvoltage from the main controller 152 to the battery controller 18, andthe other cut-off switch 156 a is provided on the conductive path 156for conducting a signal voltage from the battery controller 18 to themain controller 152. The cut-off switches 154 a, 156 a are controlled bythe main controller 152. When the main controller 152 determines thatthe high-voltage electric tool 100 has not been used for a predeterminedtime, the main controller 152 switches off the cut-off switches 154 a,156 a, thereby electrically disconnecting the battery controllers 18from the main controller 152. As a result, leakage current is preventedfrom flowing for too long of a time between the battery controllers 18and the main controller 152, thereby preventing the low-voltage batterypack 10 from being excessively discharged. The cut-off switches 154 aand 156 b are electrically connected between the main controller 152 andrespective battery controllers 18 via the respective wires 154, 156,through which a leakage current may flow.

It should be understood that the arrangement of the cut-off switch(es)of the present teachings is not limited to the arrangement shown in thepresent embodiment. For example, if there are a plurality of wires,through which a leakage current may possibly flow between the maincontroller 152 and one battery controller 18, the cut-off switch(s) maybe provided in one or some, but not all, of the conductive paths. Inanother alternative embodiment, in which a plurality of battery packs isconnected to the main controller, the cut-off switch(s) may be providedbetween the main controller 152 and only one or some of the batterypacks (e.g., only the first battery pack #1 or the second battery pack#2).

As described hereinabove, when the charge state of the cells 16 isdetected as having decreased below a pre-determined threshold, thebattery controller 18 outputs an autostop signal to the autostopterminal 26, which is electrically connected to the autostop terminal136. The autostop signal outputted from the battery controller 18 isinput into the main controller 152 via the conductive path 156. The maincontroller 152 receives the autostop signal from the battery controller18 and outputs an autostop signal to the gate-voltage-controllingtransistor 192. In this case, the autostop signal outputted by the maincontroller 152 is conducted to the gate of the gate-voltage-controllingtransistor 192 via an autostop signal input/output circuit 144. As aresult, the gate-voltage-controlling transistor 192 is turned on (i.e.becomes conductive), the power FET 194 is shut off, and current supplyto the motor 176 is stopped. The low-voltage battery pack 10 is thusprevented from being over or excessively discharged.

In addition, when the main controller 152 receives the autostop signalfrom the battery controller 18, the indicator (LED of indicationcircuit) 160 is preferably illuminated. In this case, the maincontroller 152 selectively illuminates only the indicator 160corresponding to the low-voltage battery pack 10 that has outputted theautostop signal. As a result, the user can immediately determine whichlow-voltage battery pack 10 requires charging.

As described hereinabove, the high-voltage electric tool 100 has twobattery interfaces 130 configured to removably receive respectivelow-voltage battery packs 10 and can simultaneously use two low-voltagebattery packs 10 as the power source. The two low-voltage battery packs10 are connected in series to the motor 176 and supply a voltage of 36volts to the motor 176. Thus, the high-voltage electric tool 100 with arated voltage of 36 volts is driven by two low-voltage battery packs 10,each having a nominal voltage of 18 volts. The user can power thehigh-voltage electric tool 100 by using already available low-voltagebattery packs 10, without having to purchase the high-voltage batterypack 30 and a charger therefor. Each low-voltage battery pack 10 alsocan be used individually as a sole power source for the low-voltageelectric tool 50. Therefore, the user can effectively use the alreadyavailable low-voltage battery packs 10 and the battery charger therefor.

FIG. 6 illustrates an example in which the electric circuit of thehigh-voltage electric tool 100 has been modified. In this modifiedexample, two bypass circuits 158 are added to the circuit shown in FIG.5. One bypass circuit 158 is provided for each respective low-voltagebattery pack 10 connected with the main controller 152. Each bypasscircuit 158 connects the positive electrode input terminal 134 a withthe negative electrode input terminal 134 b for one battery pack 10 viaa diode 158 a. Thus, the bypass circuit 158 connects the positiveelectrode output terminal 24 a with the negative electrode outputterminal 24 b of each low-voltage battery pack 10 via the diode 158 a.In this embodiment, one bypass circuit 158 is provided for each of thebattery packs 10 connected with the main controller 152. Note that thearrangement of the bypass circuit(s) of the present teachings is/are notlimited to the above embodiment. For example, the bypass circuit may beprovided between only some of the battery packs (e.g., only the firstbattery pack #1 or the second battery pack #2).

The anode of the diode 158 a is connected to the negative electrodeinput terminal 134 b, and the cathode of the diode 158 a is connected tothe positive electrode input terminal 134 a. Therefore, electric currentnormally does not flow in the diode 158 a, and the positive electrodeoutput terminal 24 a and the negative electrode output terminal 24 b ofthe low-voltage battery pack 10 are electrically disconnected. However,when the low-voltage battery pack 10 becomes over-discharged and areverse voltage is generated across the output terminals 24 a, 24 b ofthe low-voltage battery pack 10, electric current is caused to flow inthe diode 158 a. Thus, the output terminals 24 a, 24 b of the batterypack 10 become electrically connected via the bypass circuit 158. As aresult, even if only one low-voltage battery pack 10 becomesover-discharged, any damage caused to that low-voltage battery pack 10can be minimized or even prevented. A fuse 158 b also may be optionallyprovided in the bypass circuit 158. In this case, if a large currentflows in the bypass circuit 158, the bypass circuit 158 will bephysically disconnected by the fuse 158 b, which has melted or otherwisebroken the connection due to the excessive current. As a result, anydamage caused to the low-voltage battery pack 10 can be minimized orprevented, for example, even when Zener breakdown occurs in the diode158 a. The fuse 158 b is preferably accessible by the user so that itcan be replaced, in case it is broken.

FIG. 7 illustrates another modified example of the electric circuit ofthe high-voltage electric tool 100. In this modified example, theattachment position of the power supply for the main controller 152 inthe circuit shown in FIG. 5 has been changed. As shown in FIG. 7, themain switch 178 is inserted between the low-voltage battery pack 10 andthe power supply circuit 142. Thus, when the main switch 178 is switchedoff, the current flow to the main controller 152 is simultaneously shutoff. As a result, the main controller 152 can be prevented fromunnecessarily consuming power in an inactive state of the high-voltageelectric tool 100.

FIG. 8 illustrates another modified example of the electric circuit ofthe high-voltage electric tool 100. In this modified example, two bypasscircuits 158 are added to the circuit shown in FIG. 7. The structure,functions, and effect of the bypass circuits 158 are same as describedwith reference to the embodiment shown in FIG. 6.

Two types of adapters 200, 300 are also disclosed in the presentteachings, namely a corded adapter 200 and an integrated adapter 300.The corded adapter 200 will be explained first with reference to FIGS.9, 10, and 11. The tool shown in FIGS. 9 and 10 corresponds to the tool70 shown in FIGS. 19-22, which was described above and is incorporatedherein by reference. As shown in FIG. 9, the adapter 200 is configuredto connect a plurality of low-voltage battery packs 10 to thehigh-voltage electric tool 70. The adapter 200 is provided with a mainbody side unit 202 configured to be detachably attached to the main body72 of the high-voltage electric tool 70, a pack side unit 206 configuredto removably receive or attach a plurality of low-voltage battery packs10, and an electric cord 204 that physically and electrically connectsthe main body side unit 202 to the pack side unit 206. An attachmenthook 206 a optionally may be provided on the pack side unit 206 toenable it to be attached to the user's clothing or belt or anotherarticle supported by the user's body, so that the adapter 200 andattached battery packs 10 can be conveniently carried during operationof the tool 70.

As shown in FIG. 10, the main body side unit 202 has an outer contourthat generally conforms to the outer contour of the high-voltage batterypack 30. A connector 220 is provided on the main body side unit 202 inthe same manner as on the high-voltage battery pack 30. The connector220 can be slidingly inserted into the battery interface 80 provided onthe main body 72 of the high-voltage electric tool 70. The connector 220includes a pair of rails 222, a positive electrode output terminal 224a, a negative electrode output terminal 224 b, and an autostop terminal226. When the main body side unit 202 is attached to the batteryinterface 80, the positive electrode output terminal 224 a of the mainbody side unit 202 is connected to the positive electrode input terminal84 a of the battery interface 80, and the negative electrode outputterminal 224 b of the main body side unit 202 is connected to thenegative electrode input terminal 84 b of the battery interface 80.Further, the autostop terminal 226 is connected to the batterycontroller input/output (autostop) terminal 86. As a result, the mainbody side unit 202 is electrically connected to the internal circuitryof the main body 72 of the high-voltage electric tool 70. Further, themain body side unit 202 has a latch member 212 that is engaged with thelatch receiving hole 88 (see FIG. 22) of the battery interface 80 and isconfigured to detachably affix the main body side unit 202 to thebattery interface 80. This engagement of the latch receiving hole 88with the latch member 212 can be released by the latch release button214.

As shown in FIG. 11, the pack side unit 206 includes two batteryinterfaces 230. Each battery interface 230 can removably receive orattach one low-voltage battery pack 10, and the low-voltage battery pack10 can be slidably received thereby. The battery interface 230 has apair of rails 232, a positive electrode input terminal 234 a, a negativeelectrode input terminal 234 b, a battery controller input/output(autostop) terminal 236 and a latch receiving hole 238. With respect tothe structure, the battery interface 230 is substantially identical tothe battery interface 60 of the low-voltage electric tool 50 explainedhereinabove with respect to FIGS. 17 and 18 and incorporated herein byreference. The two battery interfaces 230 are arranged side by side onthe lower surface of the pack side unit 206 and the low-voltage batterypacks 10 are respectively inserted therein in the same direction. Thetwo low-voltage battery packs 10 attached to the pack side unit 206 areconnected in series to the positive electrode output terminal 224 a andthe negative electrode output terminal 224 b of the connector 220. As aresult, the two low-voltage battery packs 10 supply current to theinternal circuitry of the main body 72 of the high-voltage electric tool70 at a voltage of about 36 volts. The adapter 200 enables the powertool 70 having the battery interface 80 dedicated for the high-voltagebattery pack 30 to be connected to the low-voltage battery packs 10 andto be driven thereby. In addition, the autostop terminal 26 of thebattery pack 10 is connected to the autostop terminal 236 of the packside unit 206.

As shown in FIG. 11, the pack side unit 206 also includes two indicators260. The two indicators 260 are respectively positioned above the twobattery interfaces 230. Each indicator 260 is for example alight-emitting diode, but may be any other device that is capable ofvisually communicating information about the status of the attachedbattery pack 10, such as one or more incandescent lamps or one or moreLCDs. The teachings concerning the indicator 160 discussed above withrespect to the embodiment of FIGS. 2-4 are equally applicable to thepresent embodiment and thus the above-teachings concerning the indicator160 are incorporated herein. Thus, for example, one indicator 260 mayindicate a charge state or level of charge of the low-voltage batterypack 10 attached to one battery interface 230, and the other indicator260 may indicate the same condition (level of charge) or anothercondition of the low-voltage battery pack 10 attached to the otherbattery interface 230. Each indicator 260 preferably indicates at leastthe charge state of its corresponding low-voltage battery pack 10. Forexample, the light-emitting diode can be illuminated when the chargestate drops below a level at which recharging becomes necessary. Likethe indicator 160, it is again preferred that the indicator 260indicates the charge state of its corresponding low-voltage battery pack10 at least in two levels. Also similar to the indicator 160, it isagain preferred that the indicator 260 indicates a temperatureabnormality of its corresponding low-voltage battery pack 10, instead ofor in addition to the charge state thereof.

The two indicators 260 are preferably arranged side by side on onesurface of the pack side unit 206 and have the same or substantially thesame indication direction (that is, the same or substantially the sameillumination direction of light-emitting diodes). Therefore, the usercan see the two indicators 260 simultaneously and can simultaneouslyrecognize the charge states of the two low-voltage battery packs 10.Further, the indicators 260 are preferably disposed above thecorresponding battery interfaces 230. Therefore, for example, if thehigh-voltage electric tool 70 abruptly stops, the user can immediatelydetermine which low-voltage battery pack 10 has experienced a problem orabnormality. The two indicators 260 can be also disposed, for example,on the main body side unit 202, rather than on the pack side unit 206.The two indicators 260 can be also arranged in other locations that canbe simultaneously viewed by the user. It is preferred that the twoindicators 260 are disposed in the same plane, so that the user cansimultaneously see the two indicators 260 from various directions.

Similar to the indicator 160, the indicator 260 can be also provided ineach low-voltage battery pack 10. As has already been explained above,the two battery interfaces 230 are arranged side by side and can receivethe low-voltage battery packs 10 in the same direction. Therefore, whenthe two low-voltage battery packs 10 are attached to the pack side unit206, the two indicators 260 are positioned side by side in the sameplane and the direction of illumination is also the same. The user canthus simultaneously view the two indicators 260 from various directions.

An exemplary electric circuit of the adapter 200 will be explained belowwith reference to FIG. 12. As will be readily understood from acomparison of FIG. 12 with FIG. 5, the circuit of the adapter 200 issubstantially identical to a part of the circuit disposed in the mainbody 102 of the above-described high-voltage electric tool 100. Morespecifically, a combination of the circuit of the main body 72 of thehigh-voltage electric tool 70 and the circuit of the adapter 200 shownin FIG. 12 is substantially identical to the circuit of the main body102 of the high-voltage electric tool 100 shown in FIG. 5 (however, thepower FET 246 is absent in FIG. 5).

First, the circuit of the main body 72 of the high-voltage electric tool70 shown in FIG. 12 will be explained. The main body 72 of thehigh-voltage electric tool 70 is provided with a motor 76, a main switch78, a speed adjusting circuit 90, a power FET 94, agate-voltage-controlling transistor 92, and a voltage division circuit96. The configurations of these components may be identical to those ofthe motor 176, main switch 178, speed adjusting circuit 190, power FET194, gate-voltage-controlling transistor 192, and voltage divisioncircuit 196 of the main body 102 of the high-voltage electric tool 100described above with reference to FIGS. 5-8 and therefore an explanationthereof is not necessary here. Two low-voltage battery packs 10 are thusconnected in series to the motor 76 via the adapter 200.

The adapter 200 is provided with a main controller 252, a power sourcecircuit 242, a shunt resistor 250, a current detection circuit 248, anautostop signal input/output circuit 244, and a fuse 262. The maincontroller 252 is electrically connected to two indicators 260. Theconfigurations of these components may be identical to those of the maincontroller 152, power source circuit 142, shunt resistor 150, currentdetection circuit 148, autostop signal input/output circuit 144,indicator 160, and fuse 162 in the main body 102 of the high-voltageelectric tool 100 and therefore an explanation thereof also is notnecessary here.

The adapter 200 is further provided with a power FET 246 between anegative electrode input terminal 234 b connected to the low-voltagebattery pack 10 and a negative electrode output terminal 224 b connectedto the high-voltage electric tool 70. Thus, two low-voltage batterypacks 10 are electrically connected to the motor 76, and a dischargecurrent produced by the two series-connected low-voltage battery packs10 flows through this circuit. The main controller 252 is connected tothe gate of the power FET 246 and can control the power FET 246. Forexample, the main controller 252 may shut off the power FET 246 when theoutput voltage of the current detection circuit 248 exceeds apredetermined value.

The functions of the power FET 246 will be explained below. When theadapter 200 is detached from the high-voltage electric tool 70, theconnector 220 of the adapter 200 is exposed. When the two low-voltagebattery packs 10 are attached to the adapter 200 in this state, avoltage of about 36 volts is generated across the positive electrodeoutput terminal 224 a and the negative electrode output terminal 224 bin the connector 220. The positive electrode output terminal 224 a andthe negative electrode output terminal 224 b are disposed in a slot ofthe adapter 200 as shown in FIG. 10. Therefore, foreign matter isgenerally prevented from coming into contact with the two outputterminals 224 a, 224 b. However, the possibility of the foreign mattercoming into contact with the two output terminals 224 a, 224 b cannot becompletely excluded. For example, if the two output terminals 224 a, 224b were to be short-circuited by foreign matter, a very large currentflow could be generated inside the low-voltage battery pack(s) 10 oradapter 200. In the circuit according to the present embodiment, thepower FET 246 is provided inside the adapter 200 so that, after theadapter 200 has been removed from the high-voltage electric tool 70, ifvery large current is detected, the circuit and thus the current flowcan be cut off by the power FET 246.

The main controller 252 is electrically connected to an autostopterminal 236 of the battery interface 230 and can receive an inputsignal voltage (for example, an autostop signal) from the batterycontroller 18 and can output a signal voltage (for example, a dischargeprotection cancellation signal) to the battery controller 18. Cut-offswitches 254 a, 256 a are provided, respectively, in a conductive path254 that conducts the signal voltage from the main controller 252 to thebattery controller 18 and in a conductive path 256 that conducts asignal voltage from the battery controller 18 to the main controller252. Further, level-shifters 254 b, 256 b are also provided in theconductive paths 254, 256, respectively, in order to adjust the voltageof signals output from the battery controller 18 of the low-voltagebattery pack 10 that is positioned on the high-voltage side, as wasdiscussed above with respect to the exemplary level shifters 154 b, 156b of FIGS. 5-8. Thus, the cutoff switches 154 a, 156 a and levelshifters 154 b, 156 b described above with respect to the high-voltageelectric tool 100 may be used without modification in the presentembodiment and therefore an explanation thereof is not necessary here.

As described hereinabove, by using the adapter 200, the high-voltageelectric tool 70 (which is designed to normally attach only one batterypack at the battery interface 80) can be operated with two low-voltagebattery packs 10. By connecting the two low-voltage battery packs 10 inseries to the motor 76, it is possible to supply a voltage of about 36volts to the motor 76. As a result, the high-voltage electric tool 70with a rated voltage of 36 volts can be driven by two low-voltagebattery packs 10, each having a nominal voltage of 18 volts. Thus, thehigh-voltage electric tool 70 can be operated using already availablelow-voltage battery packs 10, without the need to purchase ahigh-voltage battery pack 30 that supplies a nominal voltage of 36 voltsor the charger therefor. Each low-voltage battery pack 10 can also beindividually used as the sole power source for the low-voltage electrictool 50, which operates with an 18 volt battery pack.

FIG. 13 illustrates a modified example of the electric circuit of theadapter 200. In this modified example, two bypass circuits 258 are addedto the circuit shown in FIG. 12. One bypass circuit 258 is provided foreach respective low-voltage battery pack 10. The bypass circuit 258includes a diode 258 a and a fuse 258 b. These bypass circuits 258 maybe identical to the bypass circuits 158 of the high-voltage electrictool 100 described above with respect to FIGS. 6 and 8 and therefore anexplanation thereof is not necessary here.

Another (integrated) adapter 300 will be explained below with referenceto FIGS. 14, 15, and 16. The tool shown in FIGS. 14-16 corresponds tothe tool 70 shown in FIGS. 19-22, which was described above and isincorporated herein by reference. As shown in FIG. 14, the adapter 300also serves to connect a plurality of low-voltage battery packs 10 tothe high-voltage electric tool 70. Similar to the adapter 200, theadapter 300 also enables the power tool 70 having the battery interface80 designed to receive the high-voltage battery pack 30 to be connectedto the low-voltage battery packs 10 and to be driven thereby. Incontrast with the above-described adapter 200, the entire circuitry forthis adapter 300 is contained within one housing. That is, the portions,which correspond to the main body side unit 202 and pack side unit 206of the above-described adapter 200, are integrated into a singlehousing. The electric circuitry of the adapter 300 may be functionallyidentical to the circuitry of the above-described adapter 200 shown inFIG. 12 or FIG. 13.

As shown in FIG. 15, the connector 220 may be provided at or on theupper surface of the adapter 300 in the same manner as the connector 220of the corded adapter 200 shown in FIG. 10. Thus, the connector 220 canbe slidingly inserted into the battery interface 80 provided on the mainbody 72 of the high-voltage electric tool 70. The connector 220 includesa pair of rails 222, a positive electrode output terminal 224 a, anegative electrode output terminal 224 b, and an autostop terminal 226.The structures of connectors 220 in the two types of adapters 200, 300may be substantially identical. Thus, when the connector 220 of theadapter 300 is attached to the battery interface 80, the positiveelectrode output terminal 224 a of the adapter 300 is electricallyconnected to the positive electrode input terminal 84 a of the batteryinterface 80, and the negative electrode output terminal 224 b of theadapter 300 is electrically connected to the negative electrode inputterminal 84 b of the battery interface 80. As a result, the adapter 300is electrically connected to the circuitry contained in the main body 72of the high-voltage electric tool 70. In addition, the autostop terminal86 is connected to the autostop terminal 226.

As shown in FIG. 16, two battery interfaces 230 are provided on thelower surface of the adapter 300 in the same manner as the batteryinterfaces 230 of the corded adapter 200 shown in FIG. 11. Each batteryinterface 230 can removably receive or attach one low-voltage batterypack 10, and the low-voltage battery pack 10 can be slidably receivedthereby. The battery interface 230 has a pair of rails 232, a positiveelectrode input terminal 234 a, a negative electrode input terminal 234b, and a latch receiving hole 238. The structures of the batteryinterfaces 230 of the two types of adapters 200, 300 may besubstantially identical. The two battery interfaces 230 are arrangedside by side on the lower surface of the pack side unit 206 and thelow-voltage battery packs 10 are respectively inserted therein in thesame direction. The two low-voltage battery packs 10 attached to theadapter 300 are connected in series to the positive electrode outputterminal 224 a and the negative electrode output terminal 224 b of theconnector 220. As a result, the two low-voltage battery packs 10 supplycurrent to the circuitry contained in the main body 72 of thehigh-voltage electric tool 70 at a voltage of about 36 volts. Inaddition, the autostop terminal 26 of the battery pack 10 is connectedto the autostop terminal 236 of the adapter 300.

As shown in FIG. 15, the adapter 300 is also provided with twoindicators 260. The two indicators 260 are disposed on the rear surface300 a of the adapter 300. The two indicators 260 are respectivelypositioned above the two battery interfaces 230. Each indicator 260comprises, e.g., a light-emitting diode or another light source, such asan incandescent light, or a display device such as an LCD, as wasdescribed above with reference to the indicator 260 of the cordedadapter 200 and the indicator 160 of the embodiment of FIGS. 2-4, whichdescription is again incorporated herein by reference. Thus, similar tothe above embodiments, the indicator 260 may indicate a charge state ofthe low-voltage battery pack 10 attached to one battery interface 230,and the other indicator 260 may indicate the same or a differentcondition of the low-voltage battery pack 10 attached to the otherbattery interface 230. The two indicators 260 are preferably arrangedside by side on the rear surface 300 a of the adapter 300. Therefore,the user can see the two indicators 260 simultaneously and cansimultaneously recognize the respective charge states or other indicatedcondition(s) of the two low-voltage battery packs 10. Further, theindicators 260 are preferably disposed above the corresponding batteryinterfaces 230. Therefore, for example, if the high-voltage electrictool 70 abruptly stops, the user can immediately determine whichlow-voltage battery pack 10 is experiencing a problem or abnormality.

As described hereinabove, by using the adapter 300, the high-voltageelectric tool 70 can be operated using two low-voltage battery packs 10.By connecting the two low-voltage battery packs 10 in series to themotor 76, it is possible to supply a voltage of about 36 volts to themotor 76. As a result, the high-voltage electric tool 70 with a ratedvoltage of 36 volts can be driven by two low-voltage battery packs 10,each having a nominal voltage of 18 volts. Thus, the high-voltageelectric tool 70 can be powered using already available low-voltagebattery packs 10, without the need to purchase a high-voltage batterypack 30 having a nominal voltage of 36 volts or a charger therefor. Eachlow-voltage battery pack 10 can be also individually used as the solepower source for the low-voltage electric tool 50.

In the present description, the representative example of thelow-voltage electric tool 50 is an electric drill, and therepresentative example of the high-voltage electric tools 70, 100 is anelectric blower (leaf blower). However, the present teachings are notparticularly limited to these types of electric tools and can be widelyapplied to a variety of types of electric tools, as was described abovein the Summary section.

Specific embodiments of the present teachings are described above, butthese embodiments merely illustrate some representative possibilitiesfor utilizing the present teachings and do not restrict the claimsthereof. The subject matter set forth in the claims includes variationsand modifications of the specific examples set forth above.

The technical elements disclosed in the specification or the drawingsmay be utilized separately or in other combinations that are notexpressly disclosed herein, but will be readily apparent to a person ofordinary skill in the art. Furthermore, the subject matter disclosedherein may be utilized to simultaneously achieve a plurality of objectsor to only achieve one object, which object(s) may not be explicitlyrecited in the present disclosure.

Although the present teachings have been described with respect to apreferred usage of lithium-ion cells, the present teachings are, ofcourse, applicable to any type of battery chemistry or technology,including but not limited to nickel-cadmium, nickel-metal-hydride,nickel-zinc, lithium iron phosphate, etc.

Further, although the representative electric power tool 100 and theadapters 200, 300 were illustrated as providing a serial connection oftwo battery packs 10, the battery interface 80 of the tool 100 or theadapters 200, 300 may, of course, be modified to connect three or morebattery packs 10 in series and/or in parallel. Moreover, the firstbattery packs 10 are not all required to have the same nominal voltageand in certain applications of the present teachings, one first batterypack 10 could have a first nominal voltage, e.g., of 12 volts, and onefirst battery pack 10 could have a second nominal voltage, e.g., of 18volts, i.e. the first and second nominal voltages of the two batterypacks 10 are different. In this case, it is preferable that the firstbattery interfaces 130, 230 are configured differently, so as to be ableto ensure that only the appropriate battery pack is attachable thereto.In addition or in the alternative, the main controller 152 of the tool70, 100 or the main controller 252 of the adapter 200, 300, and itssupporting circuitry, may be configured to recognize battery packshaving different nominal voltages and process signals outputted from therespective CPUs of the battery packs appropriately.

The adapters 200, 300 may be modified to only provide a voltagelevel-shifting function and the tool motor controlling function may beperformed by an integrated circuit, e.g., a microprocessor, located inthe main body 72, 100 of the tool 70, 100. For example, the adapters200, 300 are not required to include the main controller 252 and insteadmay include, e.g., only the level-shifters 254 b, 256 b and/or thecut-off switches 254 a, 256 a. Naturally, the adapters 200, 300 may alsoinclude the diode(s) 258 a, the fuse(s) 258 b and the indicators 260. Insuch embodiments, the functions of the main controller 252 are performedby circuitry located in the main body 72, 100 of the tool 70, 100. Inthis case, the level-shifters 254 b, 256 b preferably supply appropriatevoltage-adjusted signals from the battery pack controllers 18 to theprocessor located in the main body 72, 102.

What is claimed is:
 1. An electric power tool comprising: a main bodysupporting a tool element; an electric motor housed in the main body andconfigured to drive the tool element, the electric motor having a ratedvoltage that is substantially equal to or greater than 36 volts; aplurality of battery interfaces, each configured to removably receiveone battery pack having a nominal voltage that is substantially equal toor greater than 18 volts, but less than 36 volts, and to electricallyconnect a plurality of attached battery packs in series with theelectric motor so as to supply 36 volts or greater to the electricmotor; and a plurality of indicators configured to respectively indicateat least a level of charge of each respective battery pack attached tothe main body, wherein the indicators are arranged so as to besimultaneously viewable in at least one direction when the plurality ofbattery packs are respectively attached to the plurality of batteryinterfaces.
 2. The electric power tool as in claim 1, wherein each ofthe plurality of indicators indicates whether or not the level of chargeof the corresponding battery pack has dropped below a predeterminedthreshold, thereby indicating the corresponding battery pack requiresrecharging.
 3. The electric power tool as in claim 1, wherein each ofthe plurality of battery packs comprises a latch configured to engage acorresponding engagement structure defined on or near the correspondingbattery interface.
 4. The electric power tool as in claim 1, wherein theplurality of battery interfaces is integrally formed on the main body.5. The electric power tool as in claim 1, wherein each battery pack hasa nominal voltage that is substantially equal to 18 volts, and theelectric motor has a rated voltage that is substantially equal to 36volts.
 6. The electric power tool as in claim 1, wherein each of theplurality of battery packs comprises a plurality of lithium-ion cellsconnected in series.
 7. The electric power tool as in claim 1, whereineach of the plurality of battery packs comprises at least fivelithium-ion cells connected in series.
 8. The electric power tool as inclaim 1, wherein the electric power tool includes a front and a rear anda center of mass, wherein the at least one of the plurality of batteryinterfaces is located rearward of the center of mass.
 9. The electricpower tool as in claim 1, wherein the electric power tool includes afront and a rear and a first center of mass when no battery packs areattached to the plurality of battery interfaces and a second center ofmass when the plurality of battery packs are attached to the pluralityof battery interfaces, and wherein a distance from the rear to the firstcenter of mass is greater than a distance from the rear to the secondcenter of mass.
 10. The electric power tool as in claim 1, wherein thetool element comprises a fan and the electric power tool is a leafblower.
 11. The power tool as in claim 1, wherein: the plurality ofbattery interfaces comprises a first battery pack interface and a secondbattery pack interface, the plurality of attached battery packscomprises a first battery pack and a second battery pack, the firstbattery pack interface comprises a first pair of guide rails configuredto slidably receive and engage corresponding rails on the first batterypack in a detachable manner and a first latch receiving hole configuredto engage with a movable latch provided on the first battery pack, thefirst latch receiving hole being disposed between longitudinal axes ofthe first pair of guide rails; the second battery pack interfacecomprises a second pair of guide rails configured to slidably and engagecorresponding rails on the second battery pack in a detachable mannerand a second latch receiving hole configured to engage with a movablelatch provided on the second battery pack, the second latch receivinghole being disposed between longitudinal axes of the second pair ofguide rails, and the first and second battery pack interfaces arearranged side by side on the tool housing such that all of thelongitudinal axes of the first and second pair of guide rails areintersected by a common plane.
 12. The power tool as in claim 11,wherein the first latch receiving hole extends perpendicular to thelongitudinal axes of the first pair of guide rails and the second latchreceiving hole extends perpendicular to the longitudinal axes of thesecond pair of guide rails.
 13. A power tool comprising: a tool housing;an electric load disposed within the tool housing and having a ratedvoltage that is substantially equal to or greater than 36 volts; a firstbattery pack interface defined on the tool housing and electricallyconnected to the electric load, the first battery pack interfacecomprising a pair of guide rails configured to slidably receive andengage corresponding rails on a first battery pack in a detachablemanner and a latch receiving hole disposed between virtual projectionsthat are respectively collinear with the pair of guide rails; a secondbattery pack interface defined on the tool housing and electricallyconnected to the electric load, the second battery pack interfacecomprising a pair of guide rails configured to slidably and engagecorresponding rails on a second battery pack in a detachable manner anda latch receiving hole disposed between virtual projections that arerespectively collinear with the pair of guide rails; the first batterypack having a pair of rails respectively engaged with the pair of railsof the first battery pack interface and a movable latch engaged with thelatch receiving hole of the first battery pack interface; the secondbattery pack having a pair of rails respectively engaged with the pairof rails of the first battery pack interface and a movable latch engagedwith the latch receiving hole of the second battery pack interface, thefirst and second battery packs each having a nominal voltage that issubstantially equal to or greater than 18 volts, but less than 36 volts;a first indicator configured to indicate at least a level of charge ofthe first battery pack when the first battery pack is attached to thetool housing; and a second indicator configured to indicate at least alevel of charge of the second battery pack while the second battery packis attached to the tool housing; wherein the first and second indicatorsare arranged so as to be simultaneously viewable in at least onedirection when the first battery pack is attached to the first batterypack interface and the second battery pack is attached to the secondbattery pack interface.
 14. The power tool as in claim 13, wherein thefirst and second battery pack interfaces are arranged side by side onthe tool housing such that all of the virtual projections of the firstand second battery pack interfaces are intersected by a common plane.15. The power tool as in claim 14, wherein each of the first and secondbattery pack interfaces further comprises a positive electrode inputterminal, a negative electrode input terminal and a battery controllerinput/output terminal, all of which are intersected by the common plane.16. The electric power tool as in claim 13, wherein the power toolincludes a front and a rear and a center of mass, wherein at least oneof the first and second battery pack interfaces is located rearward ofthe center of mass.
 17. The electric power tool as in claim 13, whereinthe power tool includes a front and a rear and a center of mass, whereinthe first and second battery pack interfaces are located rearward of thecenter of mass.
 18. The electric power tool as in claim 13, wherein thepower tool includes a front and a rear and a first center of mass whenno battery packs are attached to the first and second battery packinterfaces and a second center of mass when first and second batterypacks are attached to the first and second battery pack interfaces, andwherein a distance from the rear to the first center of mass is greaterthan a distance from the rear to the second center of mass.
 19. Theelectric power tool as in claim 13, wherein the electric load comprisesa fan and the electric power tool is a leaf blower.